Save the state of StartUpBudgetLengthActivity

In order for the user not to choose the dates again in case they exit out
of the activity - the activity needs to save its state.

- Save the state of StartUpBudgetLengthActivity via saving the values in
  SharePrefs.
Save state of StartUpBudgetAmountActivity

- Implement saving of the state of StartUpBudgetAmountActivity in case the
  user wants to navigate back to other start up activities.
Implement checks in StartUpBudgetAmount

-implement budget checks in startUpBudgetAmountActivity